Method and apparatus for direct bonding two bodies

Abstract

Bodies of at least one material are held in a contacting holder 12 in a vacuum chamber. The surfaces of the bodies are cleaned by a low energy ion etching. Water vapor from a pure water bottle is supplied through a nozzle as a water molecule beam so that water molecules and hydroxide groups are chemically adsorbed on the surfaces of the bodies. A plasma beam or microwaves are applied to the surfaces of the bodies to remove the water molecules and leave only hydroxide groups remaining on the surfaces. The holder is operated to bring the surfaces of the bodies into contact with each other, to thereby obtain direct bonding of the bodies.

We claim: 
     
       1. A method for direct bonding of two bodies of at least one material, said method comprising: a first step of preparing two bodies having surfaces which complementarily correspond to each other and which can come into intimate contact with each other and cleaning said surfaces of the bodies in a vacuum atmosphere;   a second step of causing said cleaned surface of at least one of said bodies to chemically adsorb hydroxide groups; and   a third step of bringing said surfaces of said bodies into contact with each other and bonding said bodies through hydrogen bonds between the hydroxide groups on said surface of said at least one body and oxygen atoms present on said surface of the other body.   
     
     
       2. A method according to claim 1, wherein said first step is conducted by one of ion etching and sputter etching. 
     
     
       3. A method according to claim 1, wherein said second step comprises a fourth step of spraying water molecules onto said at least one surface of said bodies in a vacuum to cause water molecules and hydroxide groups adsorbed onto said at least one surface of said bodies, and   a fifth step of applying an energy to said at least one surface of said bodies, said energy being only as high as necessary to remove the water molecules from said at least one surface of said bodies so that hydroxide groups remain on said at least one surface of said bodies.   
     
     
       4. A method according to claim 3, wherein said fifth step is conducted by applying one of a plasma beam and a microwave to said at least one surface of said bodies. 
     
     
       5. A method according to claim 3, wherein said fifth step is conducted by applying one of radio frequency waves and a DC voltage onto at least one of said bodies so as to decompose and remove the water molecules from said at least one surface of said bodies by the effect of an electromagnetic field generated by the radio frequency waves or DC voltage, and so that hydroxide groups remain on said at least one surface of said bodies. 
     
     
       6. A method according to claim 1, wherein said second step comprises creating a plasma beam comprising ions of an inert gas for generating plasma and at least one hydrogen-containing reactive gas, and   applying said plasma beam to said at least one surface of said bodies to cause said at least one surface of said bodies to adsorb hydroxide groups.   
     
     
       7. A method according to claim 1, wherein said second step comprises applying one of radio frequency waves and a direct electric current to water molecules to decompose the water molecules into hydroxide groups by an electromagnetic field generated thereby or a plasma energy generated by said electromagnetic field, and spraying the formed hydroxide groups onto said at least one surface of said bodies to adsorb the formed hydroxide groups by said at least one surface of said bodies. 
     
     
       8. A method according to claim 1, wherein said second and third steps comprise: applying water molecules onto said at least one surface of said bodies in a vacuum to cause the water molecules to be adsorbed onto said at least one surface of said bodies, then   bringing said surfaces of the bodies into contact with each other with the water molecules being present between said surfaces of the bodies, and then   applying one of a radio frequency and a direct electric current to said bodies to remove water molecules from the surfaces of the bodies by the effect of an electromagnetic field generated thereby, to thereby bond said bodies.   
     
     
       9. A method according to claim 1, wherein said bodies have surfaces which are preliminarily mirror polished. 
     
     
       10. A method according to claim 1, wherein said bodies have surfaces which are split from a body without a plastic deformation and which complementarily correspond to each other and can come into intimate contact with each other. 
     
     
       11. A method according to claim 1, wherein said second step comprises introducing water vapor into the vacuum atmosphere, ionizing the water vapor and spraying the ionized water vapor onto said at least one surface of said bodies, to thereby cause the hydroxide groups to be adsorbed onto said at least one surface of said bodies. 
     
     
       12. A method according to claim 1, wherein said third step comprises after said second step, bringing said surfaces of the bodies into contact with each other by means of contacting equipment, and   heating said bodies in a heating chamber to remove water molecules present between the contacted surfaces of the bodies.   
     
     
       13. An apparatus for direct bonding of two bodies of at least one material, comprising: a vacuum chamber;   a first means for holding two bodies to be bonded while surfaces of the bodies are exposed and for, by subsequent operation, bringing said surfaces of the bodies into contact with each other in the vacuum chamber;   a second means for causing the surfaces of the bodies to adsorb hydroxide groups in the vacuum chamber; and   a third means for operating said first means to bring said surfaces of the bodies into contact with each other in the vacuum chamber.   
     
     
       14. An apparatus according to claim 13, wherein said second means comprises a means for spraying water molecules onto at least one of the surfaces of the bodies, and   a means for applying a beam of an inert gas plasma generated by microwaves to said at least one surface of the bodies.   
     
     
       15. An apparatus according to claim 13, wherein said second means comprises a plasma generating means for generating plasma of an inert gas and applying a beam of the generated plasma to at least one of the surfaces of the bodies, and   a means for introducing at least one reactive gas including hydrogen to said plasma generating means to generate said plasma beam comprising ions of said at least one gas.   
     
     
       16. An apparatus according to claim 13, wherein said second means comprises a means for spraying water molecules onto at least one of the surfaces of the bodies, and   a means for applying a radio frequency wave or direct electric current to said water molecules spraying means so as to decompose the water molecules to hydroxide groups by a magnetoelectric field of said radio frequency waves or direct electric current or by a plasma energy generated by said magnetoelectric field and for spraying the formed hydroxide groups from a nozzle of said spraying means to the at least one of the surfaces of the bodies.   
     
     
       17. An apparatus according to claim 13, wherein said second means comprises a means for spraying water molecules onto at least one of the surfaces of the bodies, and   a means for applying a radio frequency wave or direct electric current through the first means to said bodies so as to decompose and remove the water molecules on said at least one of the surfaces of the bodies.   
     
     
       18. An apparatus according to claim 13, wherein said second means comprises a pure water tank from which water vapor is introduced into the vacuum chamber, and a means for ionizing the water vapor, and spraying said ionized water vapor onto said at least one of the surfaces of the bodies so that hydroxide groups are adsorbed on the said at least one of the surfaces of the bodies.